Expansions, Utilities and Variants

RetroBoom

Dux Britainniarum

Dux Britainniarum by Two Fat Lardies - narrative, light rules set for miniature campaigns set in the Dark Ages. Specifically 450-600 AD, the Arthurian era with the immigration/invasion of the Saxons. Later there may be campaign rules for multiple kingdoms, sieges and other forces (Jutes, Angles, Picts, Vikings etc).

Three Plains

I recently found this - Three Plains a wargame with free rules and free to print off models to play the game with, which is a very cool thing! Looking at its rules, it seem to be a lot like Warhammer Fantasy in some ways. Here's the link for you guys to check it out for yourselves.
Get Three Plains a bit like Warhammer Fantasy

Rudis

Doctor Who Miniatures Game

Giant Monster Rampage

Play Aids and useful information for playing this miniatures based game.

Original

Morituri Nolumus Mori

My incredibly detailed swordfighting rules. Apologies to Terry Pratchett for stealing his Latin phrase “we who are about to die don't want to”. These rules are about as realistic as I can get them and still be playable. They're meant to be a replacement for whatever roleplaying game you're using so you'll need to adapt them to whatever abstractions are used in your system.